After 60 years, Alvin and the Chipmunks are, as their catchy TV theme song perpetually promises, coming on stronger than ever before.

Late last year, the harmonizing rodents with a penchant for hula hoops and harmonicas celebrated their sixth decade since their breakout hit “The Chipmunk Song (Christmas Don’t Be Late)” — a novelty tune crafted by the inventive music producer Ross Bagdasarian Sr. — put them on the pop culture map in 1958. Over the years the Chipmunks, as with the greatest pop artists, would successfully reinvent themselves — as animated TV characters, movie stars and masters of virtually every musical genre.

That enviable track record has finally earned a star on the Walk of Fame for Alvin, Simon and Theodore, something that resonates deeply for Ross Bagdasarian Jr. and his wife, Janice Karman, the keepers of the Chipmunks’ creative flame since Bagdasarian Sr.’s death in 1972.

The 1960s-era empire became one of multimedia, with merchandise and a primetime animated series in addition to the albums. But Bagdasarian Jr. believed in a longer life for his father’s creations.

“He told me that he just wanted to honor his father for a year and bring those characters back,” says Karman, who teamed with her husband in an effort to launch a late ’70s Chipmunks revival.

The couple met resistance at nearly every turn, with the property pooh-poohed as a fad of the baby boomer past, but “there’s something about being too stupid to not give up,” says Bagdasarian Jr. “We just believed in it. And the more people told us no, the more we committed to it.”

That tenacity led to the album “Chipmunk Punk” in 1980, cannily applying the nostalgic Chipmunk formula to semi-edgy contemporary cover songs. A sensation, it swiftly led to a string of follow-up music and an updated animated series that became a staple of Saturday morning TV.

“I was a little nervous about changing the look from the ’60s to the ’80s,” says Bagdasarian Jr. “But we changed the vernacular. We updated the world.”

In the process, the couple learned just how adaptable the Chipmunks were for the changing times.

Karman tweaked the band’s look for the Reagan era, zeroing in on their individual personas and insisting on grounded stories that offered relatable, universal themes.

“I have to thank Ross Sr. because the core of this is this relationship between Dave and Alvin,” she says. “When I was a kid and I first heard ‘The Chipmunk Song,’ what I loved about it was that there’s a little being who is so exasperating, but you like him. I just wanted to make sure that we retained that likability and the essence of that relationship.”

Now fully iconic, the Chipmunks defied expectations again by thriving in a quartet of CG/live action feature films, beginning with 2007’s “Alvin and the Chipmunks,” and in the current, slightly reimagined CG TV series that launched in 2015.

Through it all, the Bagdasarian family has remained the Chipmunks’ hands-on creative caretakers — the couple even provides all of the main characters’ voices.

“It’s homemade,” Karman says. “We have our recording studio in the home. We do all our production in the home. All of our production is sent overseas for animation, but everything else is done here.”

The most important part of furthering the Alvin and the Chipmunks brand while still honoring its decades-long legacy, Bagdasarian Jr. says, is doing “something that continues to keep the franchise fresh and alive and in new directions.

“That’s always top of mind for us: how can we present these characters in a new, fresh, fun way?”